Varying the height of a vehicle's suspension is a common aftermarket modification. Height adjustment can be achieved by adjusting the height of the springs by a mechanical arrangement or in the case of pneumatic or hydraulic suspension arrangements by pneumatic or hydraulic means. Some modern SUVs and cars use height adjustability as part of an active suspension system, for example, the Mercedes-Benz Active Body Control system. Some city buses also incorporate height adjustment to allow elderly or handicapped passengers to board and alight more easily.
Lifting a vehicle's suspension increases the height between the axle and the underside of the body providing more ground clearance to the bodywork of the vehicle. This allows larger wheels or tyres to be fitted, which, in turn, increases ground clearance.
For street vehicles, a kit for lifting a vehicle's suspension will typically comprise longer struts, longer springs and remounted shocks. For off-road vehicles having beam axles and transfer cases, the suspension system is typically a leaf-spring system, so the kit will comprise a set of blocks that fit between the beam axles and the bottom of the leaf spring. Alternatively, some kits have blocks which lower the spring mounts themselves so that the spring-to-axle joint is not changed. Lift kits are mainly used on trucks and SUVs.
Lowering a vehicle's suspension is another common modification and generally lowers the centre of gravity and thus improves handling. Lowering kits typically comprise shorter, stiffer springs and gas shocks. In addition to providing height adjustment, these kits typically allow for adjustment of rebound dampening and compression dampening.
The most common form of suspension adjustment mechanism comprises a stationary, externally threaded tube inside the coil spring. The base of the tube is usually attached to a lower suspension control arm. The body of the shock absorber may pass through the tube, in which case, the tube may be attached to the shock absorber or may be integrally formed with part of the shock absorber.
The external thread of the tube normally engages a matching outer threaded collar that supports the base of the coil spring. In other arrangements, the threaded collar mounts on top of the coil spring with the internal tube attached to the above frame of the vehicle.
Such adjustment mechanisms are raised and lowered by use of a C-shaped wrench to engage the outer circumference of the coil seat collar so that it can be rotated. Three or more sets of engaging, rotating then re-engaging of the C-shaped wrench may be required per revolution of the collar. This is a very labor and time intensive process and is made more so by difficulty in rotating the outer threaded collar. This difficulty arises due to the collar's close proximity to other suspension components which means that the wrench may only be able to be used over a short travel and with little leverage.
One specific form of varying suspension height is by preloading the suspension and is commonly carried out on motorcycles. In this context, preload is used to adjust the initial position of the suspension with the weight of the motorcycle and rider acting on it. Both the front forks and rear shock or shocks can be adjusted on most modern motorcycles. Some motorcycles have externally accessible preload adjustments. Typically, this is a screw-type adjustment that moves a backing plate inside the fork against the top of the fork spring. The farther down the adjuster is screwed, the more force is applied to the spring, and the higher the preload.
The present invention seeks to provide a suspension height adjustment mechanism which will overcome or substantially ameliorate at least some of the deficiencies of the prior art, or to at least provide an alternative.
It is to be understood that, if any prior art information is referred to herein, such reference does not constitute an admission that the information forms a part of the common general knowledge in the art, in Australia or any other country.